X-ray Quasi-Periodic Eruptions from two previously quiescent galaxies

A. Malyali; A. Merloni; A. Rau; A. Schwope; C. Markwardt; D.A.H. Buckley; D. Bogensberger; D. Pasham; E. Kara; G. Lamer

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X-ray Quasi-Periodic Eruptions from two previously quiescent galaxies

R. Arcodia, A. Merloni, K. Nandra, J. Buchner, M. Salvato, D. Pasham, R. Remillard, J. Comparat

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G. Lamer, G. Ponti, A. Malyali, J. Wolf, Z. Arzoumanian, D. Bogensberger, D.A.H. Buckley, K. Gendreau, M. Gromadzki, E. Kara, M. Krumpe, C. Markwardt, M. E. Ramos-Ceja, A. Rau, M. Schramm, A. Schwope

High Energy Astrophysical Phenomena · Submitted 27 Apr 2021

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim Instead, QPEs might be driven by an orbiting compact object.

how it is stated · speculative 0.96 read the record →

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arXiv ID2104.13388 (version 1)

Pith IDQMS5ZLQE, Pith's permanent record of this paper and its review

CitationA. Malyali, A. Merloni, A. Rau, A. Schwope, C. Markwardt, D.A.H. Buckley, D. Bogensberger, D. Pasham, E. Kara, G. Lamer, G. Ponti, J. Buchner, J. Comparat, J. Wolf, K. Gendreau, K. Nandra, M. E. Ramos-Ceja, M. Gromadzki, M. Krumpe, M. Salvato, M. Schramm, R. Arcodia, R. Remillard, Z. Arzoumanian. "X-ray Quasi-Periodic Eruptions from two previously quiescent galaxies." arXiv:2104.13388 (2021). https://pith.science/paper/QMS5ZLQE

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The paper's own sentences, arranged. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

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Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 7,047 input tokens.

What the abstract itself states, as probabilities: claims first 0.13 · states limitation 0.47 · human participants 0.01 · controlled comparison 0.10 · randomized assignment 0.01 · states quantitative result 0.25 · compares with prior results 0.93 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; show every role.

Quasi-Periodic Eruptions (QPEs) are extreme high-amplitude bursts of X-ray radiation recurring every few hours and originating near the central supermassive black holes in galactic nuclei. It is currently unknown what triggers these events, how long they last and how they are connected to the physical properties of the inner accretion flows. Previously, only two such sources were known, found either serendipitously or in archival data, with emission lines in their optical spectra classifying their nuclei as hosting an actively accreting supermassive black hole. Here we present the detection of QPEs in two further galaxies, obtained with a blind and systematic search over half of the X-ray sky. The optical spectra of these galaxies show no signature of black hole activity, indicating that a pre-existing accretion flow typical of active nuclei is not required to trigger these events. Indeed, the periods, amplitudes and profiles of the newly discovered QPEs are inconsistent with current models that invoke radiation-pressure driven accretion disk instabilities. Instead, QPEs might be driven by an orbiting compact object. Furthermore, their observed properties require the mass of the secondary object to be much smaller than the main body and future X-ray observations may constrain possible changes in the period due to orbital evolution. This scenario could make QPEs a viable candidate for the electromagnetic counterparts of the so-called extreme mass ratio inspirals, with considerable implications for multi-messenger astrophysics and cosmology.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	Quasi-Periodic Eruptions (QPEs) are extreme high-amplitude bursts of X-ray radiation recurring every few hours and originating near the central supermassive black holes in galactic nuclei.	background 1.00	0.06	0.03	asserted 1.00
s1	It is currently unknown what triggers these events, how long they last and how they are connected to the physical properties of the inner accretion flows.	gap 1.00	0.04	0.02	asserted 0.95
s2	Previously, only two such sources were known, found either serendipitously or in archival data, with emission lines in their optical spectra classifying their nuclei as hosting an actively accreting supermassive black hole.	background 0.96	0.04	0.02	asserted 1.00
s3	Here we present the detection of QPEs in two further galaxies, obtained with a blind and systematic search over half of the X-ray sky.	contribution 0.95	0.97	0.11	asserted 1.00
s4	The optical spectra of these galaxies show no signature of black hole activity, indicating that a pre-existing accretion flow typical of active nuclei is not required to trigger these events.	result 0.62	0.92	0.41	hedged possibility 0.53
s5	Indeed, the periods, amplitudes and profiles of the newly discovered QPEs are inconsistent with current models that invoke radiation-pressure driven accretion disk instabilities.	interpretation 0.66	0.80	0.15	asserted 0.97
s6	Instead, QPEs might be driven by an orbiting compact object.	interpretation 1.00	0.34	0.38	speculative 0.96
s7	Furthermore, their observed properties require the mass of the secondary object to be much smaller than the main body and future X-ray observations may constrain possible changes in the period due to orbital evolution.	interpretation 0.72	0.70	0.13	asserted 0.70
s8	This scenario could make QPEs a viable candidate for the electromagnetic counterparts of the so-called extreme mass ratio inspirals, with considerable implications for multi-messenger astrophysics and cosmology.	interpretation 1.00	0.18	0.26	hedged possibility 0.99

What kind of paper the classifier reports this is: empirical study 1.00 · evidence from observation or experiment 0.93.

What was examined, and what was not

sources read

arXiv listing abstract v1

not examined

full text
figures and tables
references and citing sentences
relations to other papers

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P abstract

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S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

The paper

Original abstract

Quasi-Periodic Eruptions (QPEs) are extreme high-amplitude bursts of X-ray radiation recurring every few hours and originating near the central supermassive black holes in galactic nuclei. It is currently unknown what triggers these events, how long they last and how they are connected to the physical properties of the inner accretion flows. Previously, only two such sources were known, found either serendipitously or in archival data, with emission lines in their optical spectra classifying their nuclei as hosting an actively accreting supermassive black hole. Here we present the detection of QPEs in two further galaxies, obtained with a blind and systematic search over half of the X-ray sky. The optical spectra of these galaxies show no signature of black hole activity, indicating that a pre-existing accretion flow typical of active nuclei is not required to trigger these events. Indeed, the periods, amplitudes and profiles of the newly discovered QPEs are inconsistent with current models that invoke radiation-pressure driven accretion disk instabilities. Instead, QPEs might be driven by an orbiting compact object. Furthermore, their observed properties require the mass of the secondary object to be much smaller than the main body and future X-ray observations may constrain possible changes in the period due to orbital evolution. This scenario could make QPEs a viable candidate for the electromagnetic counterparts of the so-called extreme mass ratio inspirals, with considerable implications for multi-messenger astrophysics and cosmology.

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References

Forward citations

Cited by 8 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Long before plunge: Uncovering intermediate-mass black holes through their inspiralling compact object companions with LISA
astro-ph.HE 2026-11 conditional novelty 7.0 of 10

LISA could discover 0.1 to 10^3 intermediate-mass black holes via gravitational waves from inspiraling compact objects, with the majority of detections arising from long-lived, non-merging systems.
Low-hard to high-soft spectral state transitions in the faintest early-X-ray-detected optical tidal disruption event TDE 2025aarm
astro-ph.HE 2026-07 unverdicted novelty 7.0 of 10

TDE 2025aarm is the faintest early-X-ray-detected optical TDE and the first thermal TDE reported to show a low-hard to high-soft X-ray state transition resembling black-hole X-ray binaries.
Self-lensing of electromagnetic counterparts to extreme mass ratio inspirals
astro-ph.HE 2026-11 conditional novelty 6.0 of 10

Self-lensing by the central supermassive black hole can make EMRI disk-crossing flares alternate bright and dim, reveal the precession period through envelope spacing, and soften the secondary peak.
EMRIs in Kerr Spacetime: The Role of Inclination Diffusion
astro-ph.GA 2026-10 accept novelty 6.0 of 10

Inclination diffusion from two-body scattering in Kerr spacetime increases the EMRI-to-plunge ratio, yielding a factor of ~2.5 rate enhancement for spinning black holes and a similar factor for relativistic vs. Newton...
Extreme mass ratio inspirals from the Hills mechanism, The eccentricity distribution of Hills EMRIs in LISA
astro-ph.HE 2026-10 conditional novelty 6.0 of 10

For a reference Milky-Way-like nuclear star cluster, Hills EMRIs have a mean eccentricity of 0.097 at LISA-band entry and 0.034 at plunge, versus 0.478 and 0.228 for classical EMRIs, and produce about 12% of the class...

Show 3 more citing papers

Quasi-periodic eruption spectral-timing: EMRIs crossing warped accretion disks
astro-ph.HE 2026-10 conditional novelty 6.0 of 10

A joint spectral-timing framework simultaneously reproduces QPE timings and quiescent disk spectra in GSN 069 and eRO-QPE2, but multimodal degeneracy prevents any unique EMRI parameter measurement.
The Delay Time Distribution of Quasi-Periodic Eruptions
astro-ph.GA 2026-08 conditional novelty 6.0 of 10

QPE host galaxies are more likely to have recently formed a large burst of stars (burst mass fraction above 1%) than TDE host galaxies or mass- and redshift-matched controls.
Black hole-accretion disk collision in general relativity: Axisymmetric simulations
astro-ph.HE 2025-04 conditional novelty 6.0 of 10

Black hole-disk collisions eject less mass than earlier models, with flare luminosity near the Eddington limit, while sustained super-Eddington accretion onto the black hole lasts for about a million Schwarzschild tim...

How later papers used it

91 later papers cite it

Evidence: substantial. 67 of the citing papers share no author with it, and 21 of those carry a confident label from Pith's citation classifier.

Pith read 19 of the 241 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

2 later papers by other authors are listed below: 2 used its data or values. 3 more papers by the same authors are listed: 3 used its data or values.

Uses its data or values 5 of 21 papers with this label · 3 by the same authors

Divided the 2 sources discovered with eROSITA by this paper by the product of the co-moving volume out to eRO-QPE1 and the density of Milky Way-like galaxies to roughly estimate the QPE occurrence fraction.

EMRI + TDE = QPE: Periodic X-ray Flares from Star-Disk Collisions in Galactic Nuclei (2023) · 0.84 · paraphrased: the licence does not allow quoting
Said that the number of QPEs N_QPE = 2 detected thus far by eROSITA in this paper requires a rate of at least 10^-7 per year for the precessing case and at least 10^-5 per year for the non-precessing case.

Interacting Stellar EMRIs as Sources of Quasi-Periodic Eruptions in Galactic Nuclei (2021) · 0.99 · paraphrased: the licence does not allow quoting

By the same authors

Taking the duty-cycle of eRO-QPE1 [ref] as a reference due to its similarities with Tormund, we find a probability of about 30% of detecting at least 20 ks of eruption in a random 30 ks exposure (to be compared with the $∼0.1%$ chance of observing the delayed X-ray TDE).

Tormund's return: Hints of quasi-periodic eruption features from a recent optical tidal disruption event (2023) (same authors) · Tormund as a QPE source · 0.97
If the energy generated due to accretion is $E_acc = ηMc^2$ with $η= 0.1$, then using a luminosity distance of 233 Mpc alongside the mean observed eruption flux of 3.4$×$10$^-13$ (see Figure [ref]) implies an X-ray (0.3–1 keV) energy release per outburst of $E ≃7×10^46$ erg (average flux$×$4$×π$(luminosity distance)$^2×(1+z=0.0505)×$(average eruption duration of 8 hours from [ref] )), and hence an accreted mass of $M_acc = E_acc/(0.1 c^2) ≃4×10^-7 M_⊙$.

Alive but Barely Kicking: News from 3+ years of Swift and XMM-Newton X-ray Monitoring of Quasi-Periodic Eruptions from eRO-QPE1 (2024) (same authors) · Repeating partial Tidal Disruption Event (TDE) · 0.93
If we assume our reported QPE timing residuals (Fig. [ref]) are associated with the disk LT precession, for $M_BH∼10^5.8 M_⊙$ [ref] , $M_D=2M_⊙$, and $R_out=100 R_g$, we can constrain (although degenerately) the SMBH spin $a$ and disk surface density profile $Σ(R)$ (Fig. [ref]).

Testing EMRI models for Quasi-Periodic Eruptions with 3.5 years of monitoring eRO-QPE1 (2024) (same authors) · Order in the recurrence times · 0.96

How the literature uses it

4 arXiv papers cite this in 10 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 5 sentences without a confident label

Contests it 1 paper

Initially, radiation-pressure disc instabilities were proposed [ref] , but the asymmetry in some of eRO-QPE1 eruptions, as well as considerations on the viscous timescales of the accretion flow, disfavoured this explanation [ref] .

Tormund's return: Hints of quasi-periodic eruption features from a recent optical tidal disruption event · Introduction · contest 0.76

Uses its data or values 1 paper

Taking the duty-cycle of eRO-QPE1 [ref] as a reference due to its similarities with Tormund, we find a probability of about 30% of detecting at least 20 ks of eruption in a random 30 ks exposure (to be compared with the $∼0.1%$ chance of observing the delayed X-ray TDE).

Tormund's return: Hints of quasi-periodic eruption features from a recent optical tidal disruption event · Tormund as a QPE source · 0.97

Compares with it 1 paper

The amplitude of the burst, $∼$125 in count rates, is large but consistent with what is seen in eRO-QPE1 [ref] .

Tormund's return: Hints of quasi-periodic eruption features from a recent optical tidal disruption event · Tormund as a QPE source · 0.94

Cites it as support 1 paper

Therefore the smallest galaxies with the lightest black holes could be the most frequent sites of the perturber–accretion disc interactions, which is observationally hinted by the recent detection of X-ray quasi-periodic eruptions in low-mass black hole systems [ref] , see also Subsections [ref] and [ref] for more details.

Stellar transits across a magnetized accretion torus as a mechanism for plasmoid ejection · Occurrence of stars in the innermost region · 0.99

Cites it as background 1 paper

To date, only four bona fide QPE sources are known: GSN 069 [ref] , RX J1301.9+2747 [ref] , eRO-QPE1 and eRO-QPE2 [ref] , along with one additional strong candidate, XMMSL1 J024916.6-041244 [ref] .

Tormund's return: Hints of quasi-periodic eruption features from a recent optical tidal disruption event · Introduction · 0.80

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